The optical diffractive (DOE)-based sensor was used to the study of the optical roughness of different carbon/graphite electrodes modified by mercury film (MFEs) and solid amalgam-alloy electrodes (S-MeAEs). The electrode surfaces were visualised by an optical metallurgical microscope. The adsorption of adenosine at the MFEs and S-MeAEs has been investigated by capacitance measurement. Some kinetics aspects, such as the influence of the surface morphology, nature of the substrate and thickness of the mercury film and amalgam-alloy on the formation of two-dimensional (2D) physisorbed adenosine adlayer on the MFEs and S-MeAEs, were studied.